John,
Yes the $40 coupon code is fine I can apply that for you when you are ready to purchase!

All necessary items for functionality are included, the only thing that may be additional is a coupler for the optical system to eliminate BMW Assist errors but it is still in testing so no worries on that for now.

Yes seat heater strip relocation is included in either brushed or black finishes.

Warranties are one year on the units and its through us. If there is an issue we can fix we will, if not we will have to send it out to Dynavin and they will fix it but the wait time is a little lengthy sometimes.

For a GB we can discuss the discounts and such further but here is what I could definitely do: